Which SCI control system is specifically designed for the protection of signals intelligence?

The correct choice is that the control system specifically designed for the protection of signals intelligence is Signals Intelligence, often abbreviated as SIGINT. This system focuses on the collection and analysis of information derived from electronic signals and communications, including encrypted data, to gather intelligence.

SIGINT encompasses both Communications Intelligence (COMINT) and Electronic Intelligence (ELINT), and it plays a vital role in national security operations by intercepting and decoding hostile communications, and monitoring electronic emissions from various sources. The emphasis on protecting SIGINT ensures that sensitive information obtained from these signals cannot be accessed or compromised by unauthorized entities, thereby safeguarding national interests.

The option regarding Special Intelligence (SI) refers to a classification used for certain types of intelligence but does not specifically target signals intelligence. While COMINT is a subset of SIGINT that deals explicitly with communications, SIGINT itself includes a broader scope that is relevant for the question. Imagery Intelligence (IMINT), on the other hand, pertains to visual data collected from various sources like satellites and aircraft, which is entirely separate from signals intelligence.